Saithe: life, behaviour and the long reads

Saithe occupy cold north-east Atlantic shelf waters, and they use the water column far more than the bottom-oriented gadoids they are grouped with.

THEY ARE SEMI-PELAGIC. Unlike cod, which relates closely to the bottom, saithe form fast-moving shoals that hunt through the water column, frequently well off the seabed and at times right at the surface. That is why they are taken on feathers and lures at all depths and why a sounder shows them as midwater marks.

HARD GROUND AND STRUCTURE CONCENTRATE THEM — reefs, wrecks, pinnacles, rocky coasts and the edges of banks — and tidal flow over that structure is what holds them there.

CURRENT IS PART OF THE HABITAT. Saithe hold in and around fast water, using the flow to intercept prey, and marks fish on a tide.

DEPTH RANGES FROM THE SHALLOW ROCKY SHORE TO SEVERAL HUNDRED METRES, and it is size-structured: small saithe are an inshore, shallow, harbour-and-rock fish, while large adults occupy deeper offshore ground.

JUVENILES ARE HEAVILY INSHORE, in kelp, around piers and along rocky coasts in numbers, where they are a familiar shore fish and an important forage species.

COLD WATER IS THE REQUIREMENT — saithe are a boreal species, most abundant in the northern part of the north-east Atlantic and scarce at the southern edge.

AND THE INSHORE AND OFFSHORE FISH ARE PRACTICALLY DIFFERENT ANIMALS: a shore angler taking small saithe from a pier and a boat angler taking large ones over a deep wreck are fishing the same species in habitats that barely overlap.

Saithe present no hazard worth writing about — no meaningful spines, no dentition, a hand and a wet cloth handle any of them — and two genuine handling problems that have nothing to do with grip.

THE FIRST IS DEPTH. Saithe come off deep wrecks and hard ground in numbers, and a fish brought up quickly from that depth arrives with an expanded swim bladder that it cannot deflate fast enough to swim back down. It floats. Where release matters — and on a species caught in the quantities saithe are caught in, it matters — the honest answers are to fish shallower ground or to return fish immediately rather than after they have been through a bucket and a photograph. A fish that has been on deck for two minutes with an expanded bladder is not going anywhere when it goes over the side.

THE SECOND IS THAT SAITHE HAVE A REPUTATION AS POOR FOOD THAT IS LARGELY MANUFACTURED BY HANDLING. The flesh is greyer than cod's, which is a fact about the fish, and it goes soft and strong-tasting quickly, which is a fact about what usually happens to it. Saithe are typically caught in numbers, piled in a fish box, left in the sun and dealt with hours later. Treated that way, any fish would be disappointing and this one is worse than most because the flesh is comparatively soft to begin with.

BLED AT ONCE AND CHILLED IMMEDIATELY, saithe is a perfectly good fish — firm, clean and well regarded in Norway and Iceland, where the handling has always been better because the fishery is commercial and the incentive is direct. The greyness cooks white.

SO THE PRACTICAL SUMMARY IS THE SAME AS FOR EVERY FAST-GROWING SHOALING PREDATOR: decide at once whether each fish is being kept or returned, act on that decision immediately, and never allow a third state in which a fish is neither being cared for nor being sent back.

Saithe present a seasonal picture that only makes sense once it is understood as two different fisheries for two different life stages of the same fish.

THE JUVENILE INSHORE FISHERY. Young saithe — the fish a Scottish or Norwegian shore angler catches in numbers — live in shallow water close to shore, around rock, weed and harbour structure, and they are available for much of the year in the north. They are shoaling, aggressive, and easy to catch, and they are the fish most people mean when they talk about saithe.

THE ADULT OFFSHORE FISHERY IS A DIFFERENT ANIMAL IN A DIFFERENT PLACE. As saithe grow they move offshore and deeper, onto wrecks, reefs and hard ground, and the fish taken there are an order of magnitude larger. That ontogenetic movement — a shift with age rather than with season — is the main structure of the species' distribution, and it is easy to mistake for a seasonal migration because the inshore fish do also move deeper in winter.

THE SEASONAL COMPONENT ON TOP OF IT IS ORDINARY. Inshore in warmer months, deeper and offshore as water cools, with spawning in deep water in the colder half of the year. It is the standard north-east Atlantic gadid pattern and it is driven by temperature and by the spawning requirement rather than by anything peculiar to the species.

TIDE, NOT SEASON, DECIDES THE ADULT FISHING. Saithe on a wreck or a reef hold in the current on the down-tide side and feed on what the flow brings past them. That is a feeding strategy that only works while water is moving, so the fish switch on and off with the tidal cycle in a way that is far more pronounced than any monthly pattern. A mark that is alive on a running tide is dead at slack water, twice a day, all year.

Which means the honest answer to when to fish for saithe is a statement about tidal state and about which fish is wanted, and the calendar is the least useful of the three.

Saithe reproduction has a geographical separation in it that most anglers never see, and it explains why the small fish and the large ones are caught in completely different places.

SPAWNING IS DEEP, OFFSHORE AND IN THE COLD MONTHS. Mature saithe gather on offshore banks and deeper shelf ground in late winter and early spring, and spawn as a broadcast event, releasing buoyant eggs into the water column. This is a cold-water, northern, shelf-scale event, and it takes place well away from the inshore rock and pier ground where the species is most familiar to shore anglers.

THE LARVAE DRIFT INSHORE AND SETTLE INTO SHALLOW WATER. After a planktonic period the young fish arrive in coastal shallows and settle into kelp, rock and shallow rough ground, where they spend their first years in dense shoals. That is the ubiquitous small saithe of harbour walls, piers and rock marks throughout the northern part of the range — an entire life stage occupying inshore habitat.

AND THEN THEY LEAVE. As they grow, saithe move progressively offshore and deeper, joining the adult shoals on the banks. So the fish a shore angler catches by the dozen and the fish a boat catches over a deep wreck are the same species at two ends of an ontogenetic migration, and there is very little overlap between them.

WHICH MAKES THE INSHORE NURSERY HABITAT A RECRUITMENT ISSUE that offshore stock management does not automatically address. Kelp and shallow rough ground condition matters to a stock that is fished a hundred miles away.

GROWTH IS FAST AND MATURITY IS REACHED WITHIN A FEW YEARS, which makes saithe more resilient than the slower northern gadoids, and shoaling behaviour makes them efficient to catch — a combination that produces a fishery capable of large landings and of rapid local depletion.

RECRUITMENT VARIES SUBSTANTIALLY BETWEEN YEARS with plankton and transport conditions, in the usual broadcast-spawner pattern, so year-class strength rather than adult abundance frequently drives what a fishery sees.

AND MANAGEMENT IS BY STOCK AREA AND IS REVISED ANNUALLY. Nothing above indicates any current limit; the competent authority does.

Saithe tackle is close enough to pollack tackle that the differences are the useful part, and there are three of them.

THE FIRST RUN IS LONGER AND MORE SUSTAINED. A pollack dives hard and briefly; a saithe dives hard and keeps swimming, and it does so with a broader tail and more stamina. That changes the drag requirement from surviving a short violent surge to controlling a longer withdrawal, and it means line capacity matters here in a way it does not for pollack in the same depth.

THE FISH ARE FREQUENTLY DEEPER AND MORE NORTHERLY, which drives the outfit up a class. Saithe on offshore banks and deep wrecks require more weight, more line and more lifting capacity simply to operate at the depth, and the shore fishery in the north is largely for the smaller inshore stage of the same species — a different and much lighter proposition, as the record's spawning section explains.

THEY SHOAL, AND SHOALING CHANGES THE TACKLE LOGIC. Saithe are taken in numbers on multi-hook traces and on jigs, and a trace holding several hooked fish applies loads that a single fish never would. Traces, swivels and knots fail in this fishery for that reason rather than because any individual fish was large.

BEYOND THAT THE PRINCIPLES ARE THE POLLACK ONES. Low-stretch line to reach the fish at depth, a leader doing mechanical shock absorption rather than concealment, enough lead for the tide and no more, and a drag set before the drop.

SAITHE ARE ALSO AN EXCELLENT LIGHT-TACKLE FISH INSHORE and are routinely under-fished as one. Small shoaling saithe over rock and kelp in the north are as good a light spinning or fly target as a temperate coast offers, and the heavy-gear reputation attaches to the offshore adults rather than to the species.

AND THEY SPOIL QUICKLY, which is a tackle-adjacent point worth making: saithe kept for the table need killing and chilling at once, and the difference between a fish handled properly and one left in a warm box is the whole of the species' reputation as food.

Grows fast, matures at four to six years and lives up to around twenty-five. Spawns in deeper water in late winter and spring, with pelagic eggs and larvae. Juveniles shoal in very shallow inshore water, including harbours and rock pools, before moving progressively deeper as they grow — which is why small saithe are the fish that so many children in northern Europe catch first.

Broadcast spawning in deep water in late winter and spring, with pelagic eggs and larvae drifting inshore. Juveniles use extremely shallow inshore habitat including harbours and rocky shores, then move deeper year by year. That ontogenetic depth shift means a shore angler and a wreck angler are catching different age classes of the same stock.

An active shoaling predator taking small fish — sand eels, herring, sprat — along with crustaceans and cephalopods, hunting in midwater and near structure rather than on the bottom. The pursuit habit and midwater feeding are why saithe respond so well to fast-retrieved lures and to jigs worked at speed, and why they are caught well off the seabed over wrecks.

Sight-dominant when hunting fast-moving prey in midwater, with the lateral line supporting in low light and at depth. Saithe respond strongly to speed and flash, which is why they are among the most reliable species on a fast-worked lure and why they will chase down a jig that a bottom-feeding gadoid would ignore.

Moves inshore in the warmer months and offshore and deeper in winter, with spawning in deep water in late winter and spring. Small fish are available from the shore for much of the year in the north. Tidal state governs the fishing on wrecks and reefs, where the fish hold in the current and feed on what is swept past.

A mainstay of northern European boat and shore fishing, taken on jigs, spinners, feathers, lures and bait over wrecks, reefs and rock. Very hard-fighting for its size and extremely reliable, which makes it the species that keeps a session going when others are quiet. Small fish from harbours and rocks introduce a great many people to sea fishing.